Boundary loop of selected faces
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Boundary Loop

Reference

Mode: Edit Mode –> Edge select mode
Menu: Select ‣ Select Boundary Loop
Select Boundary Loop does the opposite of Select Loop Inner-Region, based on all regions currently selected, it selects only the edges at the border(contour) of these islands. It can operate in any select mode, but when in Face mode it will switch to Edge select mode after running.

All this is much more simple to illustrates with examples:



The steps I took to use Select boundary loop in version blender 2.77  


Hit Tab to enter edit mode.
Make sure you are in select face mode.
Select the faces to be converted to edge boundary selection.  
Hit Ctrl + E and select "Select Boundary loop"  
That's all.  




If your command isn't there, make sure you downloaded the official release.